1. Field of the Invention
The present invention provides for microparticles and methods of making such microparticles for protecting encased bioactive substances from heat, humidity, oxidation and gastric incursions.
2. Related Background Art
A common difficulty associated with the incorporation of functional substances and/or drugs in food products is loss of activity with time, decomposition during the food manufacturing process and/or the destruction during passage of the product through the organism's digestive tract. The harsh environment of some food processes, like milling, mixing, baking, and extrusion, can destroy many bioactive substances before they become finished food products. This is especially true for enzymes and vitamins that are sensitive to most types of conventional food processing. Therefore, the food industry is continuously searching for new compositions and methods that protect bioactive compounds against decomposition during processing, storage, and gastric transit.
Additional problems result from the interaction between the desired bioactive compounds and other food components, such as metal chelators, surfactants, hygroscopic ingredients, etc. (Choe and Min, 2006). One method to protect and enhance the retention and appropriate release of a bioactive substance is encapsulation. Encapsulation is also used to protect the bioactive substance from oxygen, water, and light, as well as to convert the substance into a free-flowing powder that can be readily incorporated into various food products. Various attempts have been made over the years to enrobe or embed bioactive agents in many different types of biopolymers or synthetic polymers, including proteins, carbohydrates, and solid fats (Nissim G., 2008).
Most methods of encapsulation utilize water-soluble carrier substances such as proteins, sugars, modified starches, and gums (PCT/US2004/004003, WO2004/082660). Typical methods of encapsulation include spray drying, air suspension coating, spray cooling and chilling, co-crystallization, and centrifugal extrusion. However, these types of encapsulation are not suitable for protecting bioactive agents in food products that contain water or have a high water activity because of oxidation and subsequent degradation of the encapsulated bioactive substances under aqueous conditions. Since water is involved in the preparation of most foods at some stage of the food manufacturing process and storage, encapsulation in water-soluble polymers has limited applicability for improving the stability of bioactive compounds, or for controlling the retention of bioactive substances and directing their release in a programmed manner.
To overcome the problem of loss of activity during processing or storage in humid environments, fat encapsulation or top-coating of the water-soluble particles with a protective layer of solid fats is sometimes used. Proposed examples of coating methods with Solid Fats include: U.S. Pat. No. 4,350,679, which discloses the application of a carnauba wax coating on a soft gel. The functionality of the wax coating is to improve shell strength and moisture resistance as described in U.S. Pat. No. 5,789,014 wherein a wax, in powder or pellet form with a melting point between 40° C. and 50° C., was heated above its melting point and used for coating in a fluidized bed coating apparatus.
U.S. Patent Application Publication No. 2006/0051425 discloses methods for microencapsulation of active ingredients in a multilayer coat. The multilayer coat composed of various waxes and gums protects the active ingredient throughout processing, formulation, and storage, and enables a controlled release of the active ingredient. U.S. Patent Application Publication No. 2007/0042184 discloses a method of spray cooling aqueous beads comprising the active ingredient that is encapsulated in or by a hydrophobic shell matrix of solid fats. However, a major problem of these types of microencapsulation is that the coat is easily ruptured when water is added during conventional food manufacturing processes. Another problem with the use of fat coating is its limitation to food products that are processed at temperatures below the melting point of the fat. For example, this process is not applicable for a food process that includes boiling, baking, spray drying, or extruding, where temperatures well over 70° C. occur because the coating fat becomes liquefied and its protective properties are lost.
The object of this invention is to provide a composition and method of encapsulating a bioactive substance that overcomes these problems.